The principal objective of this research is to develop bioerodible drug delivery devices that release a therapeutic agent in response to an external signal. Activation of the device will be achieved by the interaction of an external molecule with an enzyme-antigen complex. This interaction will lead to the dissociation of the complex, activation of the enzyme and ultimately a pH change which will activate erosion of a hydrophobic polymer containing the drug. Two specific systems are being developed: 1) release of a narcotic antagonist in response to external opiates, and 2) release of a contraceptive agent in response to human chorionic gonadotrophin. These systems represent models for devices activated by a small molecule and a macromolecule.